Mutual Post-Quantum Auth over IKEv2 – IPsec Series, Part 8

In Part 7 we minted post-quantum certificates and weighed them. But certificates sitting in a folder are only half the fun. Time to do the job they were born for: prove identity. We’ll stand up two containers, each holding a certificate, and watch them prove who they are to each other before the tunnel comes up. That’s mutual authentication, over a real IKEv2 handshake.

And we’ll do it twice, and the progression is the whole point:

1. Classical ECDSA (today’s real-world posture), on stable strongSwan.
2. Post-quantum ML-DSA (the bleeding edge), on an experimental branch.

This Part uses the authentication/ lab: its own little stack, separate from the key-exchange one. Only Docker required.

Clone the repo

Grab the repo and step into this lab’s directory. All commands below run from ipsec/authentication/:

git clone https://github.com/juliogomez/pqc.git
cd ipsec/pqc/authentication

How the trust works

Both peers trust one tiny Certificate Authority we spin up just for the lab. The CA signs two leaf certificates (one per peer), and each peer gets the CA cert pre-installed so it can verify the other side. During the handshake each peer sends only its own leaf cert; the CA is already known to both. (That keeps the on-the-wire bytes down, which matters a lot once the certs go post-quantum, as Part 7 showed so clearly.) A helper script, gen-certs.sh, does all the minting; you just tell it which algorithm to use.